Rotary cutting tool with enhanced coolant delivery

ABSTRACT

A rotary cutting tool includes a main body, a shank portion having a rearward end, and a flute portion having a forward end with one or more flanks. One or more connecting fluid holes are in fluid communication with a central fluid hole and terminates at a flank at the forward end of the cutting tool. One or more twisted fluid holes extend through a lobe in the flute portion and terminates at a flank at the forward end of the cutting tool. A cross-sectional shape of the connecting fluid holes and the twisted fluid holes is selected to provide enhanced delivery of fluid to the cutting edge. In one aspect, the rotary cutting tool is a modular drill and the flute portion has a pocket for holding a replaceable cutting insert.

FIELD OF THE INVENTION

In general, the invention relates to a rotating cutting tool, and moreparticularly, to a rotating cutting tool with a primary, central fluidhole and a secondary fluid hole for each flute, each hole having across-sectional shape that is selected for providing enhanced fluiddelivery.

BACKGROUND OF THE INVENTION

Material removal operations can generate heat at the interface betweenthe cutting insert and the workpiece. Typically, it is advantageous toprovide coolant to the vicinity of the interface between the cuttinginsert and the workpiece.

Even though some prior art arrangements deliver coolant, it remainshighly desirable to provide a rotary cutting tool, such as a drill, andthe like, that delivers fluid in an efficient manner to the interfacebetween the cutting tool and the workpiece without significantlyaltering the performance and properties, such as torsional stiffness,and the like, of the cutting tool.

Thus, there is a need to provide improved fluid flow withoutsignificantly altering the performance and properties of the rotarycutting tool.

SUMMARY OF THE INVENTION

The problem of improving fluid delivery in a rotary cutting tool issolved by providing a central fluid hole and one additional fluid holefor each flute, wherein the central fluid hole has a largercross-sectional area than the twisted fluid hole in each flute.

The fluid flow rate can be substantially improved when fluid holes arestrategically placed in areas of low stress. The method of the inventioninvolves defining the central hole size and shape (round, elongated,tri-lobed) and then adding one or more holes for each flute that adaptedin shape to low stress areas of the drill. The principles of theinvention can be applied to modular or indexable drills by communicatingthe central, main fluid hole to the peripheral ones by means of crossholes or 3D printing. Additive manufacturing would also allow theprinciples of the invention to be applied to carbide drills.

In one aspect, a rotary cutting tool comprises a main body, a shankportion having a rearward end, and a flute portion having a forward endwith one or more flanks. The flute portion has a plurality of flutesseparated by lobes. The flute portion is integral and adjacent the shankportion in an axial direction of the main body. A central fluid holeextends along a central, rotational axis, RA, from the rearward end,through the shank portion, partly into the flute portion, and terminatesat a predetermined distance, DT, from the forward end. One or moreconnecting fluid holes are in fluid communication with the central fluidhole and terminate at a flank at the forward end of the flute portionfor supplying fluid to one or more cutting edges of the flute portion.One or more twisted fluid holes extend from the rearward end, throughthe shank portion, through a lobe in the flute portion, and terminate ata flank at the forward end of the flute portion for supplying fluid toone or more cutting edges of the flute portion. A cross-sectional areaof the central coolant fluid hole is larger than a cross-sectional areaof one or more of the twisted fluid holes. The central coolant fluidhole has a non-circular cross-sectional shape; and each of the twistedfluid holes has a non-circular cross-sectional shape.

In another aspect, a rotary cutting tool comprises a main body, a shankportion having a rearward end, and a flute portion having a forward endwith one or more flanks. The flute portion has one or more flutesseparated by lobes. The flute portion is integral and adjacent the shankportion in an axial direction of the main body. The flute portionincluding a pocket portion for holding a cutting insert. A central fluidhole extends along a central, rotational axis, RA, from the rearwardend, through the shank portion, partly into the flute portion, andterminates at a predetermined distance, DC, from a base surface of thecutting insert. One or more connecting fluid holes are in fluidcommunication with the central fluid hole and terminate at a flank ofthe cutting insert for supplying fluid to one or more cutting edges ofthe cutting insert. One or more twisted fluid holes extend from therearward end, through the shank portion, through a lobe in the fluteportion, and terminate at a flank of the cutting insert for supplyingfluid to one or more cutting edges of the cutting insert. Across-sectional area of the central coolant fluid hole is larger than across-sectional area of one or more of the twisted fluid holes. Thecentral coolant fluid hole has a non-circular cross-sectional shape; andeach of the twisted fluid holes has a non-circular cross-sectionalshape.

BRIEF DESCRIPTION OF THE DRAWINGS

While various embodiments of the invention are illustrated, theparticular embodiments shown should not be construed to limit theclaims. It is anticipated that various changes and modifications may bemade without departing from the scope of this invention.

FIG. 1 is a front view of a rotary cutting tool, such as a drill withthree flutes, according to an embodiment of the invention;

FIG. 2 is a top view of the three-flute drill illustrated in FIG. 1;

FIG. 3 is a partially enlarged view of a flute portion of thethree-flute drill illustrated in FIG. 1 having a total of six openingsin the three flank surfaces;

FIG. 4 is a partially enlarged view of another flute portion of thethree-flute drill illustrated in FIG. 1 having a total of three openingsin the three flank surfaces;

FIG. 5 is a cross-sectional view of a three-flute drill taken along lineX-X of FIG. 1 showing the cross-sectional shape of Variation A having acentral fluid hole with a circular cross-sectional shape and threetwisted fluid holes with a circular cross-sectional shape according toan embodiment of the invention;

FIG. 6 is a cross-sectional view of a three-flute drill taken along lineX-X of FIG. 1 showing the cross-sectional shape of Variation B having acenter fluid hole with a triangular cross-sectional shape and threetwisted fluid holes with an elongate (i.e., non-circular)cross-sectional shape according to another embodiment of the invention;

FIG. 7 is a cross-sectional view of a three-flute drill taken along lineX-X of FIG. 1 showing the cross-sectional shape of Variation C having acenter fluid hole and three twisted fluid holes, all holes with acircular cross-sectional shape and the center fluid hole having a largerdiameter than the twisted fluid holes according to another embodiment ofthe invention;

FIG. 8 is a cross-sectional view of a three-flute drill taken along lineX-X of FIG. 1 showing the cross-sectional shape of Variation D having acenter fluid hole and three twisted fluid holes, all holes with acircular cross-sectional shape and the same diameter according toanother embodiment of the invention;

FIG. 9 is a cross-sectional view of a three-flute drill taken along lineX-X of FIG. 1 showing the cross-sectional shape of Variation E having acenter fluid hole with a triangular cross-sectional shape and threetwisted fluid holes with a “D-shaped” (i.e., non-circular)cross-sectional shape according to another embodiment of the invention;

FIG. 10 is a cross-sectional view of a three-flute drill taken alongline X-X of FIG. 1 showing the cross-sectional shape of the centralfluid hole and the twisted fluid holes of the drill of the invention;

FIG. 11 is a cross-sectional view of a three-flute drill taken alongline X-X of FIG. 1 showing the cross-sectional shape of the centralfluid hole and the twisted fluid holes of the drill of the invention;

FIG. 12 is a cross-sectional view of a three-flute drill taken alongline X-X of FIG. 1 showing the cross-sectional shape of the centralfluid hole and the twisted fluid holes of the drill of the invention;

FIG. 13 is a side view of a rotary cutting tool, such as a modular drillwith two flutes, according to an embodiment of the invention;

FIG. 14 is a side view of a cutting insert according to an embodiment ofthe invention;

FIG. 15 is a bottom view of the cutting insert of FIG. 14;

FIG. 16 is a cross-sectional view of the cutting insert taken along line16-16 of FIG. 15.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1-4, a rotary cutting tool 10 is shown accordingto an embodiment of the invention. In the illustrated embodiment, therotary cutting tool 10 comprises a drill 10 provided with three cuttingedges 12 and three flutes 18. The drill 10 also includes a shank portion14 having a rearward end 15 and a flute portion 16 having a forward end13 that are integral and adjacent to each other in an axial direction ofa main body 17. The forward end 13 of the drill 10 has a cutting tip 24.

Although the rotary cutting tool 10 comprises a drill in the illustratedembodiment, it should be appreciated that the principles of theinvention can be applied to any desirable rotary cutting tool in whichfluid is supplied between the cutting tool/workpiece interface.

The description herein of specific applications should not be alimitation on the scope and extent of the use of the cutting tool.

Directional phrases used herein, such as, for example, left, right,front, back, top, bottom and derivatives thereof, relate to theorientation of the elements shown in the drawings and are not limitingupon the claims unless expressly recited therein. Identical parts areprovided with the same reference number in all drawings.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about”, “approximately”, and “substantially”, are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value. Here and throughout thespecification and claims, range limitations may be combined and/orinterchanged, such ranges are identified and include all the sub-rangescontained therein unless context or language indicates otherwise.

Throughout the text and the claims, use of the word “about” in relationto a range of values (e.g., “about 22 to 35 wt %”) is intended to modifyboth the high and low values recited, and reflects the penumbra ofvariation associated with measurement, significant figures, andinterchangeability, all as understood by a person having ordinary skillin the art to which this invention pertains.

For purposes of this specification (other than in the operatingexamples), unless otherwise indicated, all numbers expressing quantitiesand ranges of ingredients, process conditions, etc., are to beunderstood as modified in all instances by the term “about”.Accordingly, unless indicated to the contrary, the numerical parametersset forth in this specification and attached claims are approximationsthat can vary depending upon the desired results sought to be obtainedby the present invention. At the very least, and not as an attempt tolimit the application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques. Further, as used in this specification and theappended claims, the singular forms “a”, “an” and “the” are intended toinclude plural referents, unless expressly and unequivocally limited toone referent.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements including that found in the measuringinstrument. Also, it should be understood that any numerical rangerecited herein is intended to include all sub-ranges subsumed therein.For example, a range of “1 to 10” is intended to include all sub-rangesbetween and including the recited minimum value of 1 and the recitedmaximum value of 10, i.e., a range having a minimum value equal to orgreater than 1 and a maximum value of equal to or less than 10. Becausethe disclosed numerical ranges are continuous, they include every valuebetween the minimum and maximum values. Unless expressly indicatedotherwise, the various numerical ranges specified in this applicationare approximations.

In the following specification and the claims, a number of terms arereferenced that have the following meanings.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where the event occurs and instances where it does not.

As used herein, the term “elongate” is defined as something that islonger than it is wide. In other words, the width is smaller than itslength.

As used herein, the term “triangular” is defined as an object having ashape like a triangle, i.e., a polygon having three sides and threecorners.

As used herein, the term “circular” is defined as an object having ashape of a circle, i.e., an object having a simple closed shape. It isthe set of points in a plane that are at a given distance from a givenpoint, the center; equivalently it is the curve traced out by a pointthat moves in a plane so that its distance from a given point isconstant. The distance between any of the points and the center iscalled the radius.

As used herein, the term “fluid” is defined as a substance that has nofixed shape and yields easily to external pressure, such as a gas or aliquid.

As used herein, the term “helical” is defined as pertaining to or havingthe form of a helix or spiral. A “helix” or “spiral” is defined as acurve in three-dimensional space formed by a straight line drawn on aplane when that plane is wrapped around a cylindrical surface of anykind, especially a right circular cylinder, as the curve of a screw. Acircular helix of radius a and slope b/a (or pitch 2πb) is described bythe following parametrization:

x(θ)=a sin θ,y(θ)=a cos θ,z(θ)=bθ.

As used herein, the phrase “helix angle” is defined as the angle betweenany helix and an axial line on its right, circular cylinder or cone. Thehelix angle references the axis of the cylinder, distinguishing it fromthe lead angle, which references a line perpendicular to the axis. Thus,the helix angle is the geometric complement of the lead angle. The helixangle is measured in degrees.

As used herein, the term “3D printing” is any of various processes inwhich material is joined or solidified under computer control to createa three-dimensional object, with material being added together, such asliquid molecules or powder grains being fused together, typically layerby layer. In the 1990s, 3D printing techniques were considered suitableonly to the production of functional or aesthetical prototypes and, backthen, a more comprehensive term for 3D printing was rapid prototyping.Today, the precision, repeatability and material range have increased tothe point that 3D printing is considered as an industrial productiontechnology, with the official term of “additive manufacturing”.

As used herein, the helix of a flute can twist in two possibledirections, which is known as handedness. Most flutes are oriented sothat the cutting tool, when seen from a point of view on the axisthrough the center of the helix, moves away from the viewer when it isturned in a clockwise direction, and moves towards the viewer when it isturned counterclockwise. This is known as a right-handed (RH) flutegeometry, because it follows the right-hand grip rule. Flutes orientedin the opposite direction are known as left-handed (LH).

As used herein, the term “hole” is defined as an opening troughsomething; a gap; a cavity or an aperture that can have anycross-sectional shape.

As used herein, the term “triangle” is defined as a polygon with threesides and three vertices. An “equilateral” triangle is defined as atriangle in which all three sides are the same length.

Referring now to FIGS. 1-3, the drill 10 is made of solid carbide andmanufactured using a 3D printing process. However, it will beappreciated that the invention can be practiced with a drill made of anydesirable material using any desirable manufacturing process. Forexample, the drill 10 can be made of a substrate of a super hard toolmaterial, such as cemented carbide, and the like, and manufactured usinga sintering process. In addition, intermetallic compounds, a diamondfilm, and the like, can be used as a hard film disposed on thesubstrate, for enhancing the cutting durability. For example, somesuitable intermetallic compounds are metals of the groups Mb, IVa, Va,and VIa of the periodic table of the elements, for example, carbides,nitrides, and carbonitrides of Al, Ti, V, Cr, etc., or mutual solidsolutions thereof and, specifically, TiAlN alloy, TiCN alloy, TiCrNalloy, TiN alloy, and the like, can be used. Although a hard film ofsuch an intermetallic compound can be disposed by a PVD method, such asan arc ion plating, sputtering, and the like, the hard film may bedisposed by another film formation method, such as a plasma CVD, and thelike. Other suitable materials and manufacturing processes areencompassed by the principles of the invention.

The flute portion 16 is provided with a plurality of flutes 18 separatedby lobes 20 for discharging chips generated by each of the cutting edges12. In other words, the drill 10 is trilobed. The flutes 18 provided inthe flute portion 16 are helical that twist clockwise around a central,rotational axis, RA, at a predetermined helix angle, HA, of about 30°,and are formed at positions point-symmetrical with respect to thecentral, rotation axis, RA. However, it will be appreciated that theinvention is not limited by the magnitude of the helix angle, HA, andthat the invention can be practiced with any desirable helix angle, HA,in a range between about greater than 0 degrees and about 75 degrees.

Although a three-flute drill is shown in the illustrated embodiment, itshould be appreciated that the invention is not limited by the number offlutes and lobes, and that the principles of the invention can bepracticed in a drill having any desirable number of flutes, such as two,four, five, six, and the like. Further, although the three-flute drill10 in the illustrated embodiment has a drill diameter, D, of about 16mm, the drill 10 may have a drill diameter of up to about 56 mm or mayhave two-stepped outer diameters (machining diameters).

One aspect of the invention is that the drill 10 can deliver anincreased amount of fluid flow through the drill 10 to the interfacebetween the drill 10 and the workpiece (not shown). Referring now toFIG. 2, the fluid can be supplied through an internal central fluid hole26 and one or more twisted fluid holes 27, 28, 29. Each twisted fluidhole 27, 28, 29 has a spiral shape that can correspond to the path ofthe flutes 18. In addition, each twisted fluid hole 27, 28, 29 emergesin an opening (not shown) in the rearward end 15 of the drill 10 influid communication with a pressurized source of fluid (not shown).

As shown in FIG. 2, the central fluid hole 26 of the drill 10 extendsalong the rotational axis, RA, from the rearward end 15 of the drill 10,through the entire shank portion 14, partly into the flute portion 16,and terminates at some distance, DT, from the forward end 13 of thedrill 10. At the distance, DT, the central fluid hole 26 branches orsplits into one or more connecting fluid holes 26 a, 26 b, 26 c in fluidcommunication with the central fluid hole 26. The central fluid hole 26and the connecting fluid holes 26 a, 26 b, 26 c can have any desirablecross-sectional shape, such as circular, non-circular, polygonal, andthe like. For example, the central fluid hole 26 can be concentric withthe rotational axis, RA, and having a circular cross-sectional shape inthe shank portion 14 and a different cross-sectional shape, such asnon-circular, polygonal, and the like, in the flute portion 16 of thedrill 10.

In one embodiment, there is a one-to-one correspondence between thetotal number of connecting fluid holes 26 a, 26 b, 26 c and the totalnumber of flutes 18. Thus, in the illustrated embodiment, there are atotal of three connecting fluid holes 26 a, 26 b, 26 c; one connectingfluid hole 26 a, 26 b, 26 c in each flute 18.

In addition, there is a one-to-one correspondence between the totalnumber of twisted fluid holes 27, 28, 29 and the total number of flutes18. Thus, in the illustrated embodiment, there are a total of threetwisted fluid holes 27, 28, 29; one twisted fluid hole 27, 28, 29 ineach flute 18, similar to the connecting fluid holes 26 a, 26 b, 26 c.It should be noted that, in all embodiments of the invention, theconnecting fluid holes 26 a, 26 b, 26 c and the twisted fluid holes 27,28, 29 have a smaller cross-sectional area than the central fluid hole26.

As shown in FIGS. 2 and 3, the forward end 13 of the drill 10 includesthree flanks 30, 32 and 34. In this illustrated embodiment, each of theconnecting fluid holes 26 a, 26 b, 26 c and each of the twisted fluidholes 27, 28, 29 emerges in an opening in each flank 30, 32, 34.Specifically, the twisted fluid holes 27, 28, 29 emerge into openings 30a, 32 a, 34 a in the flanks 30, 32, 34, respectively. Similarly,connecting fluid holes 26 a, 26 b, 26 c emerge into openings 30 b, 32 b,34 b in the flanks 30, 32, 34, respectively.

Each connecting fluid hole 26 a, 26, 26 c may extend in a linear orcurved fashion from the central fluid hole 26 to its respective opening30 b, 32 b, 34 b. Alternatively, the connecting fluid holes 26 a, 26 b,26 c may have a spiral shape that can correspond to the path of theflutes 18, similar to the twisted fluid holes 27, 28, 29.

In the embodiment shown in FIGS. 2 and 3, there are a total of sixopenings 30 a, 30 b, 32 a, 32 b, 34 a, 34 b formed in the three flanks30, 32, 34 at the forward end 13 of the drill 10. In other words, eachconnecting fluid hole 26 a, 26 b, 26 c and each twisted fluid hole 27,28, 29 emerge into its own respective opening. However, it should beappreciated that the invention is not limited by the number of openingsin the flanks and that the invention can be practiced with a differentnumber of openings in the flanks.

Referring now to FIG. 4, an alternative embodiment of the invention isshown in which the three flanks have a total of three openings 30 c, 32c, 34 c. Specifically, the connecting fluid hole 26 a merges with thetwisted fluid hole 27 to emerge into the opening 30 c in the flank 30.Similarly, the connecting fluid hole 26 b merges with the twisted fluidhole 28 to emerge into the opening 32 c in the flank 32. Likewise, theconnecting fluid hole 26 c merges with the twisted fluid hole 29 toemerge into the opening 34 c in the flank 34.

CAE Analysis of Fluid Flow Rate

A CAE analysis of a several variations of a three-flute drill having adrill diameter, D, of about 16 mm was performed. Each variation isdescribed in Table I below. FIGS. 5-9 are cross-sectional views ofdifferent variations of the three-flute drill taken along a plane X-X(FIG. 1) orthogonal to the rotational axis, RA, for explaining across-sectional shape of the central fluid hole 26 and/or the twistedfluid holes provided in the flute portion 16 of the drill 10. VariationsA-E of the drill 10 of the invention are shown in FIGS. 5-9,respectively.

TABLE I Description of Variations Variation FIG. # Description A 5 Onecentral circular-shaped hole with a diameter of 3.1 mm and oneelongated- shaped hole in each flute B 6 One central triangular-shapedhole and one elongated-shaped hole in each flute C 7 One centralcircular-shaped hole with a diameter of 3.1 mm and one circular-shapedhole in each flute with a diameter of 2.0 mm D 8 One central 2.205 mmdiameter hole and one 2.205 mm diameter hole in each flute E 9 Onecentral triangular-shaped hole and one semi-circular-shaped hole in eachflute

The results of the CAE analysis are shown in Table II below.

TABLE II Results Flow Coolant Body Rate @ area Volume 20 bar % Variation(mm²) % A (mm³) % V (kg/s) Flow Reference 13.63 100.0% 4715.8 100.0%0.567 100% A 16.86 123.7% 4554.2 96.6% 0.725 128% B 17.24 126.5% 4534.896.2% 0.751 132% C 16.97 124.5% 4548.3 96.4% 0.712 125% D 16.12 118.3%4591.5 97.4% 0.666 117% E 17.34 127.2% 4531.9 96.1% 0.754 133%

It should be noted that the reference cutting tool (not shown) has onecircular-shaped hole in each flute with a diameter of 2.405 mm produceda flow rate of 0.576 kg/s at a pressure of 20 bar and was used as astandard flow rate of 100% for comparing to the Variations A-E of theinvention. As stated above, the central fluid hole 26 of the drill 10 ofthe invention in all the Variations A, B, C and E had a largercross-sectional area than the twisted fluid holes 27, 28, 29 in eachlobe 20, except for Variation D in which all the coolant holes (main,central hole and secondary holes) where circular in cross-sectionalshape with the same diameter of about 2.265 mm.

As shown in FIG. 5, the three-flute drill 10 of Variation A has acentral fluid hole 26 with a circular cross-sectional shape and adiameter of about 3.1 mm and three elongated-shaped (i.e., non-circular)twisted fluid holes 27, 28, 29. It should be noted that the centralfluid hole 26 is concentric with the rotational axis, RA. In thisexample, the drill 10 produced a flow rate of about 0.725 kg/s, which isan increase of about 128% as compared to the flow rate of referencecutting tool.

As shown in FIG. 6, the three-flute drill 10 of Variation B has a centerfluid hole 26 that transitions from a substantially circularcross-sectional shape to a triangular cross-sectional shape and threeelongated-shaped (i.e., non-circular) twisted fluid holes 27, 28, 29.The center fluid hole 26 has a larger cross-sectional area than each ofthe twisted fluid holes 27, 28, 29. It should be noted that the centralfluid hole 26 is concentric with the rotational axis, RA. In thisexample, the drill 10 produced a flow rate of about 0.751 kg/s, which isan increase of about 132% as compared to the flow rate of referencecutting tool, while reducing the volume of the drill body 17 by about4%.

As shown in FIG. 7, the three-flute drill 10 of Variation C has a centerfluid hole 26 with a circular cross-sectional shape and three twistedfluid holes 27, 28, 29 with a circular cross-sectional shape. The centerfluid hole 26 has a larger cross-sectional area than each of the twistedfluid holes 27, 28, 29. It should be noted that the central fluid hole26 is concentric with the rotational axis, RA. In this example, thedrill 10 produced a flow rate of about 0.712 kg/s, which is about a 125%increase in the flow rate as compared to reference cutting tool.

As shown in FIG. 8, the three-flute drill 10 of Variation D has a centerfluid hole 26 with a circular cross-sectional shape and three twistedfluid holes 27, 28, 29 with a circular cross-sectional shape. The centerfluid hole 26 has a same cross-sectional area than each of the twistedfluid holes 27, 28, 29. It should be noted that the central fluid hole26 is concentric with the rotational axis, RA. In this example, thedrill 10 produced a flow rate of about 0.666 kg/s, which is about a 117%increase in the flow rate as compared to reference cutting tool.

As shown in FIG. 9, the three-flute drill 10 of Variation E has a centerfluid hole 26 that transitions from a substantially circularcross-sectional shape to a triangular cross-sectional shape and threetwisted fluid holes 27, 28, 29 with a non-circular cross-sectionalshape. Specifically, each twisted fluid hole 27, 28, 29 is generally“D-shaped” with a substantially planar wall portion 27 a, 28 a, 29 a anda curved wall portion 27 b, 28 b, 29 b. In this embodiment, each planarwall portion 27 a, 28 a, 29 a is radially inward (i.e. closer to therotational axis, RA) with respect to each curved wall portion 27 b, 28b, 29 b. Similar to other variations, the center fluid hole 26 has alarger cross-sectional area than each of the twisted fluid holes 27, 28,29. It should be noted that the central fluid hole 26 is concentric withthe rotational axis, RA. In this example, the drill 10 produced a flowrate of about 0.754 kg/s, which is about a 133% increase in the flowrate as compared to the reference cutting tool. It should be noted thatthe highest flow rate was produced by the three-flute drill 10 ofVariation E.

In summary, all the Variations A-E of the three-flute drill 10 of theinvention produced a significantly increased flow rate as compared tothe reference cutting tool.

It should be appreciated that the principles of the invention are notlimited to the cross-sectional shape variations discussed above, andthat the invention can be practiced with the central fluid hole 26 andthe twisted fluid holes 27, 28, 29 having other variations ofcross-sectional shapes.

Referring now to FIG. 10, the three-flute drill 10 of the invention isidentical to the three-flute drill 10 shown in FIG. 9, except that thetwisted fluid holes 27, 28, 29 are rotated 180 degrees with respect tothe twisted fluid holes 27, 28, 29 of the three-flute drill 10 shown inFIG. 9.

It should be noted that finite element analysis (FEA) has demonstratedthat in overall, the total maximal deformation in the three-flute drill10 shown in FIG. 9 is smaller (i.e., the torsional stiffness is greater)than that in the three-flute drill 10 shown in FIG. 10 in which thesubstantially planar wall portions 27 a, 28 a, 29 a are radially outward(i.e. farther away from the rotation axis, RA) than the curved wallportions 27 b, 28 b, 29 b.

Referring now to FIG. 11, the three-flute drill 10 of the invention canhave a central fluid hole 26 that transitions from a substantiallycircular cross-sectional shape to a triangular cross-sectional shape andthree twisted fluid holes 27, 28, 29 having a substantiallytriangular-shaped cross section. Specifically, each triangular-shapedtwisted fluid hole 27, 28, 29 is defined by three side walls 27 c, 28 c,29 c and three vertices 27 d, 28 d, 29 d. In this embodiment, one of theside walls 27 c, 28 c, 29 c is radially inward (i.e. closer to therotational axis, RA) with respect to each vertex 27 d, 28 d, 29 d.Similar to other variations, the center fluid hole 26 has a largercross-sectional area than each of the twisted fluid holes 27, 28, 29.Similar to all other variations, the central fluid hole 26 has a largercross-sectional area than the twisted fluid holes 27, 28, 29. It shouldbe noted that the central fluid hole 26 is concentric with therotational axis, RA.

Referring now to FIG. 12, the three-flute drill 10 of the invention isidentical to the three-flute drill 10 shown in FIG. 11, except that thetwisted fluid holes 27, 28, 29 are rotated 180 degrees with respect tothe twisted fluid holes 27, 28, 29 of the three-flute drill 10 shown inFIG. 11.

It should be noted that finite element analysis (FEA) has demonstratedthat in overall, the total maximal deformation in the three-flute drill10 shown in FIG. 11 is smaller (i.e., the torsional stiffness isgreater) than that in the three-flute drill 10 shown in FIG. 12 in whichthe one of the vertices 27 d, 28 d, 29 d is radially inward (i.e.,closer to the rotational axis, RA) than each of the side walls 27 c, 28c, 29 c.

As mentioned above, the shank portion 14 and the flute portion 16 areintegral and adjacent to each other in an axial direction of a main body17. However, it should be appreciated that the principles of theinvention can be practiced with a modular drill.

Referring now to FIGS. 13-16, a rotary cutting tool 100, such as amodular drill, for conducting cutting operations on a workpiece (notshown) when the rotary cutting tool 100 is rotated about a central,longitudinal axis, RA, is shown according to an exemplary embodiment ofthe invention. Like reference numbers for the drill 10 are increased by100 for the modular drill 100. Thus, although not shown in FIG. 13, themodular drill 100 has a central fluid hole 126 and twisted fluid holes127, 128 that are identical to the central fluid hole 26 and twistedfluid holes 27, 28 of the drill 10. Although depicted as a modular drillin the exemplary embodiment described herein, it is to be appreciatedthat the principles of the invention described herein are applicable toother rotary cutting tools, such as, for example, without limitation, amilling tool, a reamer, a tap, an end mill, and the like.

The rotary cutting tool 100 is generally cylindrical and includes afirst or forward end 113 and an opposite, second or rear end 114. Therotary cutting tool 100 has a tool body 117 that includes a pocketportion 119 proximate the first end 113 for securely holding areplaceable cutting insert 150, and a flute portion 116 including aplurality of helical chip flutes 118 separated by lobes 120 extendingrearwardly from the first end 113 of the flute portion 116 to the shankportion 114. Similar to the twisted fluid holes 27, 28, 29 in the lobes20 of the three-flute drill 10, the flute portion 116 has twisted fluidholes 127, 128 (FIG. 16) in the lobes 120. The tool body 117 alsoincludes a shank portion 114 proximate the second end 115 for mountingthe rotary cutting tool 100 in a chuck mechanism of a machine tool (notshown).

In the illustrated embodiment, the rotary cutting tool 100 includes twoflutes 118 and two lobes 120. However, it should be appreciated that theinvention is not limited by the number of flutes 118 and lobes 120, andthat the invention can be practiced with a rotary cutting tool havingany desirable number of flutes 118 and lobes 120, such as three, four,five, six, seven, eight, and the like.

Each chip flute 118 allows chips formed by the cutting edges 112 of therotary cutting tool 100 to exit from the flute portion 116 during acutting operation. Each chip flute 118 has a helical geometry or patternand are disposed at a helix angle, HA, relative to the rotational axis,RA. In one embodiment, for example, the helix angle, HA, is at or about30 degrees (+/−2 degrees). However, it will be appreciated that theinvention is not limited by the magnitude of the helix angle, HA, andthat the invention can be practiced with any desirable helix angle, HA,in a range between about greater than 0 degrees and about 75 degrees.

Referring now to FIGS. 14-16, the replaceable cutting insert 150 has afront cutting part 152 and a coupling pin 154 extending axially awayfrom the front cutting part 152 (thus, in an axially rearwarddirection). The front cutting part 152 of the cutting insert 150 definesa cutting diameter, DC. On its circumference, the cutting insert 150 hasan outer peripheral surface 156 that is interrupted by opposite-facingflutes 158 that start in the cutting insert 150 and continuously mergeinto the helical flutes 118 disposed in the flute portion 116 of themain body 117.

In the exemplary embodiment, the flutes 158 are substantially helical inshape. The coupling pin 154 of the cutting insert 150 extends in theaxial rearward direction with respect to the front cutting part 152. Thecoupling pin 154 is offset in a radially inward direction from the outerperipheral surface 156. The replaceable cutting insert 150 also includesa base surface 160 with a central fluid hole 126 in fluid communicationwith the central fluid hole 26 (not shown in FIG. 13) in the fluteportion 116 of the main body 117 for providing fluid to the cuttingedges 112 of the cutting insert 150. In the illustrated embodiment, thefluid opening 126 may have an identical or different cross-sectionalshape as the central fluid hole 126 in the flute portion 116 of the mainbody 117 to provide increased flow rate to the cutting edges, ascompared to conventional cutting inserts with a circular cross-sectionalshape.

The central fluid hole 126 of the drill 100 extends along the rotationalaxis, RA, from the rearward end 115 of the drill 100, through the entireshank portion 114, and through the entire flute portion 116 and into thepocket portion 119 a predetermined distance, DB. As shown in FIG. 16,the central fluid hole 126 branches or splits at the predetermineddistance, DB, from the base surface 160 into one or more connectingfluid holes 126 a, 126 b.

In one embodiment, the total number of connecting fluid holes 126 a, 126b corresponds to the total number of flutes 118. Thus, in theillustrated embodiment, there are a total of two connecting fluid holes126 a, 126 b. The connecting fluid holes 126 a, 126 b can have anydesirable cross-sectional shape, such as circular, non-circular,polygonal, and the like.

Referring now to FIG. 16, the fluid can also be supplied through the oneor more twisted fluid holes 127, 128. In one embodiment, the totalnumber of twisted fluid holes 127, 128 corresponds to the total numberof flutes 118. Thus, in the illustrated embodiment, there are a total oftwo twisted fluid holes 127, 128. Each twisted fluid hole 127, 128 has aspiral shape that can correspond to the path of the flutes 118. Inaddition, each twisted fluid hole 127, 128 emerges in an opening (notshown) in the rearward end 115 of the drill 100 in fluid communicationwith a pressurized source of fluid (not shown).

As shown in FIG. 16, the cutting insert 150 includes two flanks 130 and132. In the illustrated embodiment of FIG. 8, each of the connectingfluid holes 126 a, 126 b and each of the twisted fluid holes 127, 128emerges in an opening in each flank 130, 132. Specifically, the twistedfluid holes 127, 128 emerge into openings 130 a, 132 b in the flanks130, 132, respectively. Similarly, connecting fluid holes 126 a, 126 bemerge into openings 130 b, 132 b in the flanks 130, 132, respectively.

Each connecting fluid hole 126 a, 126 b may extend in a linear fashionfrom the central fluid hole 126 of the cutting insert 150 to itsrespective opening 130 b, 132 b. Alternatively, the connecting fluidholes 126 a, 126 b may have a spiral shape that can correspond to thepath of the flutes 118, similar to the twisted fluid holes 127, 128.

In the embodiment shown in FIGS. 14-16, there are a total of fouropenings 130 a, 130 b, 132 a, 132 b formed in the flanks 130, 132 of thecutting insert 150. In other words, each connecting fluid hole 126 a,126 b and each twisted fluid hole 127, 128 emerge into a respectiveopening. However, it should be appreciated that the invention is notlimited by the number of openings in the flanks and that the inventioncan be practiced with a different number of openings in the flanks.Similar to the embodiment shown in FIG. 3, for example, the connectingfluid hole 126 a may merge with the twisted fluid hole 127 and emerge ina single opening in the flank 130 of the cutting insert 150. Likewise,the connecting fluid hole 126 b may merge with the twisted fluid hole128 and emerge in a single opening in the flank 132 of the cuttinginsert 150.

In each of the drills 10, 100 of the invention, the total length of thecentral fluid hole 26, 126 is larger in cross-sectional area than eachof the connecting fluid holes 26 a, 26 b, 26 c, 126 a, 126 b and thetwisted fluid holes 27, 28, 29, 127, 128 and is equal to at least 60% ofthe total length of each flute 18, 118 of the drill 10, 100. Inaddition, the length of the central fluid hole 26, 126 and the length ofthe connecting fluid holes 26 a, 26 b, 26 c, 126 a, 126 b is in a rangebetween about 60% and 90% of the total length of each flute 18, 118.

As described above, a drill 10, 100 of the invention delivers fluid inan efficient manner to the interface between the cutting tool and theworkpiece without significantly altering the performance and properties,such as torsional stiffness, and the like, of the drill 10, 100, ascompared to conventional drills.

The patents and publications referred to herein are hereby incorporatedby reference.

Having described presently preferred embodiments the invention may beotherwise embodied within the scope of the appended claims.

1. A rotary cutting tool, comprising: a main body; a shank portionhaving a rearward end; a flute portion having a forward end with one ormore flanks, the flute portion having a plurality of flutes separated bylobes, the flute portion integral and adjacent the shank portion in anaxial direction of the main body; a central fluid hole extending along acentral, rotational axis, RA, from the rearward end, through the shankportion, partly into the flute portion, and terminating at apredetermined distance, DT, from the forward end; one or more connectingfluid holes in fluid communication with the central fluid hole andterminating at a flank at the forward end of the flute portion forsupplying fluid to one or more cutting edges of the flute portion; andone or more twisted fluid holes extending from the rearward end throughthe shank portion, through a lobe in the flute portion, and terminatingat a flank at the forward end of the flute portion for supplying fluidto one or more cutting edges of the flute portion, wherein across-sectional area of the central coolant fluid hole is larger than across-sectional area of one or more of the twisted fluid holes; whereinthe central coolant fluid hole has a non-circular cross-sectional shape;and wherein each of the twisted fluid holes has non-circularcross-sectional shape.
 2. The rotary cutting tool of claim 1, whereinthe one or more flutes are formed with a helix angle, HA, with respectto a center rotational axis, RA, of the rotary cutting tool. 3.(canceled)
 4. A rotary cutting tool, comprising: a main body; a shankportion having a rearward end; a flute portion having a forward end withone or more flanks, the flute portion having a plurality of flutesseparated by lobes, the flute portion integral and adjacent the shankportion in an axial direction of the main body; a central fluid holeextending along a central, rotational axis, RA, from the rearward end,through the shank portion, partly into the flute portion, andterminating at a predetermined distance, DT, from the forward end; oneor more connecting fluid holes in fluid communication with the centralfluid hole and terminating at a flank at the forward end of the fluteportion for supplying fluid to one or more cutting edges of the fluteportion; and one or more twisted fluid holes extending from the rearwardend through the shank portion, through a lobe in the flute portion, andterminating at a flank at the forward end of the flute portion forsupplying fluid to one or more cutting edges of the flute portion,wherein a cross-sectional area of the central coolant fluid hole islarger than a cross-sectional area of one or more of the twisted fluidholes, and wherein one of the one or more connecting fluid holes and oneof the one or more twisted fluid holes emerge in the flank at theforward end of the flute portion.
 5. A rotary cutting tool, comprising:a main body; a shank portion having a rearward end; a flute portionhaving a forward end with one or more flanks, the flute portion having aplurality of flutes separated by lobes, the flute portion integral andadjacent the shank portion in an axial direction of the main body; acentral fluid hole extending along a central, rotational axis, RA, fromthe rearward end, through the shank portion, partly into the fluteportion, and terminating at a predetermined distance, DT, from theforward end; one or more connecting fluid holes in fluid communicationwith the central fluid hole and terminating at a flank at the forwardend of the flute portion for supplying fluid to one or more cuttingedges of the flute portion; and one or more twisted fluid holesextending from the rearward end through the shank portion, through alobe in the flute portion, and terminating at a flank at the forward endof the flute portion for supplying fluid to one or more cutting edges ofthe flute portion, wherein a cross-sectional area of the central coolantfluid hole is larger than a cross-sectional area of one or more of thetwisted fluid holes, and wherein the central fluid hole has a triangularcross-sectional shape, and wherein the one or more twisted fluid holeshas a different non-circular cross-sectional shape than the centralfluid hole.
 6. The rotary cutting tool of claim 1, wherein the centralfluid hole has a triangular cross-sectional shape, and wherein the oneor more twisted fluid holes are “D-shaped” in cross section.
 7. Therotary cutting tool of claim 1, wherein the rotary cutting toolcomprises a drill. 8-14. (canceled)
 15. The rotary cutting tool of claim4, wherein the one or more flutes are formed with a helix angle, HA,with respect to a center rotational axis, RA, of the rotary cuttingtool.
 16. The rotary cutting tool of claim 4, wherein the central fluidhole has a non-circular cross-sectional shape, and wherein the one ormore twisted fluid holes have a non-circular cross-section shape. 17.The rotary cutting tool of claim 16, wherein the central fluid hole hasa triangular cross-sectional shape, and wherein the one or more twistedfluid holes are “D-shaped” in cross section.
 18. The rotary cutting toolof claim 4, wherein the rotary cutting tool comprises a drill.
 19. Therotary cutting tool of claim 5, wherein the one or more flutes areformed with a helix angle, HA, with respect to a center rotational axis,RA, of the rotary cutting tool.
 20. The rotary cutting tool of claim 5,wherein the one or more twisted fluid holes are “D-shaped” in crosssection.
 21. The rotary cutting tool of claim 5, wherein the rotarycutting tool comprises a drill.